text: import requests
  from bs4 import BeautifulSoup
  import pymongo
  import re
  
  start_url = 'https://cs.58.com/sale.shtml'
  url_host = 'https://cs.58.com'
  
  headers = {'user-agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.121 Safari/537.36'}
  
  
  channel_list = []
  
  
  def get_channel_urls(url):
      html = requests.get(url, headers=headers)
      soup = BeautifulSoup(html.text, 'html.parser')
      infos = soup.select('ul > li > ul > li > b > a')
  
      for (info) in zip(infos):
          # print(url_host + info[0].get('href'))
          channel_list.append(url_host + info[0].get('href'))
  
  
  get_channel_urls(start_url)
  
  
  # if __name__ == '__main__':
  #
  #     get_channel_urls(start_url)
  
  
  